This invention relates to a device having multiple acoustic transducers that may share a single acoustic port.
In order for the sound generated or received by an acoustic transducer of a device to propagate between the transducer and the outside of the casing of the device (in either direction), an acoustic port or vent, typically in the form of a hole or grille, is typically provided in the casing. Devices may have multiple acoustic transducers. For example, a mobile telephone may have both an earpiece speaker (hereinafter referred to as a “receiver”) and a speakerphone or hands-free speaker (hereinafter referred to as a “speaker”), as well as a microphone. Similarly, a media player may have multiple speakers for stereo sound reproduction at different frequency ranges (e.g., woofers for bass frequencies).
As a definitional matter, “transducer” as used herein refers to a physical element that vibrates, rather than to any associated electrical element. Thus, a multi-coil speaker, for example, that has one cone or membrane but two or more driver coils, is considered one transducer.
Providing a separate acoustic port for each transducer may adversely affect the appearance of the device, and may even compromise structural integrity if the number of transducers is large. Additionally, each transducer is normally associated with a front acoustic volume and a back acoustic volume. Each acoustic port, front volume and back volume should be designed to provide an acoustic impedance and frequency response that match their associated transducer. If the number of transducers is large, having a front volume, back volume and port tuned to each transducer may be impractical in small handheld devices, such as mobile telephones or multi-media devices.